Red light running characteristics and rates

Turning off the cameras: Red light running characteristics and rates

A team of psychologists from Old Dominion University, led by Bryan E. Porter, had a rare chance to study how drivers adjust their behavior in the presence (or absence) of red-light cameras. In 2005, the Virginia legislature allowed the state law permitting the cameras to expire. (The law has since been reinstated.) Porter and colleagues, who had been studying red-light cameras in the state anyway, designed a new set of observations at intersections where the cameras were set to go dark.

The researchers focused on eight intersections in southeast Virginia: four in Virginia Beach with red-light cameras that would expire with the law, and four others (two in that city and two in Newport News) where cameras didn’t exist. They recorded the light status of the final car to cross through an intersection — documenting only those cars that went straight — with a particular focus on the period just before and after the cameras turned off.

In nearly 2,800 light cycles, about a quarter of all last cars to enter the intersection went through on green, and 63 percent on yellow. The remaining 12 percent crossed on red — but when the cameras were still on, that rate was only 3 percent. (At intersections that never had cameras, the last-driver-through crossed on red 14 to 15 percent of the time.)

That finding alone wasn’t terribly surprising: when punishment for a behavior goes from nearly certain to random at best, you expect the behavior to increase. What intrigued (and unsettled) the researchers was how quickly drivers reverted to red-light running form. In the immediately aftermath of the law’s expiration, the risk of someone running a red light at an intersection was three times higher than it had been when cameras were on.

A year later it was four times higher, with all risk reductions having been erased, the researchers report in an upcoming issue of the journal Accident Analysis & Prevention.

Porter and Colleagues findings suggest red-light running reductions are likely to recidivate quickly, and certainly within a year, once cameras go dark. While more research is important, our findings should give pause to those wishing to remove the technology without significant scientific reasoning for doing so.